1. Field of the Invention
The present invention is generally related to a cooling system for an outboard motor and, more particularly, to a cooling system that causes cooling water to flow through a reservoir that is in thermal communication with an oil sump and which surrounds a portion of an exhaust conduit.
2. Description of the Related Art
Those skilled in the art of cooling systems of marine propulsion devices and, more particularly, the relationship between the cooling system and both the exhaust and lubricating systems are familiar with many different processes and apparatus for causing cooling water to flow in thermal communication with both the exhaust passage of the outboard motor and the oil reservoir.
U.S. Pat. No. 4,498,875, which issued to Watanabe on Feb. 12, 1985, describes an outboard motor. Water-cooled, four-cycle internal combustion engines are used for outboard motors. In each embodiment described in this patent, an arrangement is provided that offers a compact nature and which uses the coolant delivered to the engine for cooling the oil in the oil pan. In addition, an arrangement is provided whereby the exhaust pipe may pass through the oil pan and yet avoid significant heat transfer from the exhaust system to the lubricating system.
U.S. Pat. No. 4,545,332, which issued to Suzuki et al. on Oct. 8, 1985, describes a water-cooled, four-cycle internal combustion engine for an outboard motor. The engine includes an exhaust arrangement wherein the exhaust gases are returned from the cylinder head to the cylinder block in proximity to a cooling jacket for cooling the exhaust gases before delivery into the lower unit. In addition, the cooling jacket and method of casting the cylinder head provides an opening in which a sacrificial anode may be placed to protect the engine from corrosion, particularly when operated in salt water.
U.S. Pat. No. 5,037,340, which issued to Shibata on Aug. 6, 1991, describes a lubricating device for a four-stroke outboard motor. An external oil reservoir is positioned externally of an engine. The reservoir is contained directly in the power head and in another embodiment, the reservoir is contained externally of the outboard motor. The use of such external positioning of the lubricant reservoirs from the driveshaft housing permits the use of a large expansion chamber for the exhaust system in the driveshaft housing.
U.S. Pat. No. 5,072,809, which issued to Shibata on Dec. 17, 1991, describes a lubricating device for a four-stroke outboard motor. A dry sump lubrication system includes a scavenge pump for drawing lubricant drained from the engine lubricating system through an inlet port and returns it to a dry sump reservoir through an outlet port and a pressure pump that draws lubricant from the dry sump lubricant reservoir through an inlet port and delivers it to the engine lubricating system through an outlet port. At least one of the ports of each of the pumps is positioned above the normal lubricant level in the lubricant reservoir when it is filled with the normal volume of lubricant so as to insure that lubricant will not drain back into the engine when the pump system is not operating.
U.S. Pat. No. 5,232,387, which issued to Sumigawa on Aug. 3, 1993, describes an exhaust device for a four-cycle outboard motor. Coolant is drawn from the body of water within which the watercraft is operated for circulation through the engine cooling system. Subsequently, the coolant is brought into proximity with an exhaust pipe extending downwardly from the engine within an encasing member. After passing downwardly along the exhaust pipe the coolant is finally directed towards an exhaust gas expansion chamber and a cooling water jacket provided around the expansion chamber. In order to prevent any of the cooling water from splashing back up against an oil reservoir, also located within the casing, a cover is provided across the tops of the expansion chamber and its accompanying cooling water jacket.
U.S. Pat. No. 5,462,464, which issued to Ming on Oct. 31, 1995, describes an outboard motor with an oil sump cooling arrangement. A driveshaft housing includes outer sidewalls extending in spaced relation to each other, a forwardly located wall extending between the outer side walls, a rearwardly located wall spaced rearwardly from the forwardly located wall and extending between the outer side walls, and a bottom wall extending between the outer side walls and between the forwardly and rearwardly located walls.
U.S. Pat. No. 5,487,688, which issued to Sumigawa on Jan. 30, 1996, describes an outboard motor having an oil tank that is contained within the driveshaft housing and which is surrounded at least in part by a water cooling jacket for maintaining the oil at an acceptable temperature. The oil tank is formed with a cavity through which an exhaust pipe passes and the area between the exhaust pipe and the oil tank forms, in at least some embodiments, an expansion chamber for silencing the exhaust gases.
U.S. Pat. No. 5,733,157, which issued to Okuzawa et al. on Mar. 31, 1998, describes a four-cycle outboard motor. The exhaust system includes an expansion chamber that is formed in the driveshaft housing of the outboard motor below an oil tank for the engine which is positioned therein. A water chamber is formed around the expansion chamber and the lower portion of the oil tank for cooling them. An above-the-water exhaust gas discharge is provided that communicates with the area above the water jacket.
U.S. Pat. No. 5,803,036, which issued to Takahashi et al. on Sep. 8, 1998, describes an engine for an outboard motor. An upper unit contains an internal combustion engine and a lower unit contains an exhaust guide. The engine has a vertically oriented crankshaft having an end extending from the bottom end of the engine. A flywheel is positioned on the crankshaft at the bottom end of the engine within a recess defined by the exhaust guide. A starter motor is positioned at the bottom end of the engine and is positioned at least partially within the exhaust guide, the motor having a gear for engaging the flywheel to start the engine.
U.S. Pat. No. 5,937,801, which issued to Davis on Aug. 17, 1999, discloses an oil temperature moderator for an internal combustion engine. A cooling system is provided for an outboard motor or other marine propulsion system which causes cooling water to flow in intimate thermal communication with the oil pan of the engine by providing a controlled volume of cooling water at the downstream portion of the water path. As cooling water flows from the outlet of the internal combustion engine, it is caused to pass in thermal communication with the oil pan. Certain embodiments also provide a pressure activated valve which restricts the flow from the outlet of the internal combustion engine to the space near the oil pan. One embodiment of the cooling system also provides a dam within the space adjacent to the outer surface of the oil pan to divide that space into first and second portions. The dam further slows the flow of water as it passes in thermal communication with the oil pan.
U.S. Pat. No. 6,367,442, which issued to Takayanagi on Apr. 9, 2002, describes a four-cycle outboard motor that has a simple construction and a compact design. The outboard motor has a crankshaft disposed substantially vertically within the engine, wherein the rotation of the crankshaft is transmitted to a valve camshaft via a looped member disposed at the bottom of the engine, comprises an oil pump disposed at a position other than the shaft center position of the crankshaft or the camshafts at the bottom of the engine, wherein either this oil sump or a tension adjustor of the looped member is disposed to the inside of the looped member in plan view while the other is disposed outside the looped member in plan view.
U.S. Pat. No. 6,655,341, which issued to Westerbeke on Dec. 2, 2003, describes an oil sump for vertically shafted engines. The sump has a housing with an upper face for sealing against a block of the engine. The sump housing defines an internal volume for containing a quantity of oil received from the engine through an oil drain opening in the upper face of the sump and defines an exhaust inlet for receiving a flow of exhaust from the engine and directing the flow of exhaust toward an exhaust outlet along an exhaust passage defined within the housing. The housing also defines a water inlet for receiving a flow of cooling water into a water passage within the housing about the exhaust passage. The sump also includes means for securely mounting the engine within a boat hull. In some marine applications, seawater or freshwater coolant is discharged into the exhaust gas stream at an attached exhaust elbow.
U.S. Pat. No. 6,699,086, which issued to Belter et al. on Mar. 2, 2004, discloses a coolant management system for a marine propulsion device. The system provides a cavity within a driveshaft housing into which an oil reservoir is disposed. A water pump draws water from a body of water and causes it to flow through various coolant passages of the marine propulsion device. After passing through these coolant passages, the water is directed through a series of containments and compartments so that the level of water within the driveshaft housing varies in depth as a function of the operating speed of the internal combustion engine. This variance in depth causes a varying degree of cooling of the oil within the oil reservoir or sump.
U.S. Pat. No. 6,913,498, which issued to Sheth on Jul. 5, 2005, discloses a marine propulsion system with a polymer composite oil sump structure. A marine propulsion system is made with an oil sump that is a polymer material that is nonanodic and nonmetallic. As a result, the possibility of a galvanic circuit being created within the structure of a driveshaft housing is significantly reduced or eliminated. The result is the enhanced operation of the marine propulsion system without corrosion and the resulting destruction of the internal components within the driveshaft housing.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be significantly beneficial if a cooling system for an outboard motor could assure that the water flowing through its passages is caused to flow without having stagnant regions where particulates and minerals can precipitate from the cooling water and become attached to the internal surfaces of those passages. In addition, it would be significantly beneficial if the idle relief exhaust passage could be provided without having to form holes radially through the walls of an internally supported exhaust conduit.